Technologies for protecting an IGBT, as an example of semiconductor switching elements, against an overcurrent are known, one of which is disclosed in Japanese Patent Application Publication No. H3-40517. Specifically, the technology disclosed in the Patent Publication performs a clamping task while the IGBT is in an on state. The clamp task is configured to clamp the voltage at the gate, i.e. the open-close control terminal, of the IGBT to a predetermined voltage or thereabout when it is determined that the level of a collector current flowing through an electrical path between the collector and emitter, i.e. the input and output terminals, of the IGBT exceeds a predetermined threshold level. This aims to limit an increase of the level of the collector current. The threshold level for the collector current is previously determined such that, if the level of the collector current exceeds the threshold level, it is possible to surely determine that a short-circuit fault has occurred in the IGBT. The technology forcibly turns off the IGBT after a predetermined time has elapsed since the level of the collector current exceeded the threshold level.